High thermoelectric performance in multiscale Ag8SnSe6 included n-type bismuth telluride for cooling application

Abstract

The efficiency of Bi2Te3 thermoelectric generators is strongly constrained by the fact that n-type alloys always perform poorly thermoelectrically compared to their p-type counterparts. Here, we report an efficient method for improving the thermoelectric performance of n-type Bi2Te2.69Se0.33Cl0.03 by incorporating Ag8SnSe6. The incorporation of Ag8SnSe6 increases the carrier effective mass as a result of dissolved Ag and Sn atoms in Bi2Te2.69Se0.33Cl0.03, which in turn enhances the Seebeck coefficient. The thermal conductivity of Bi2Te2.69Se0.33Cl0.03 also decreases due to multiscale phonon scattering from both the residual Ag8SnSe6 second phase and point defects. Consequently, we achieve a high ZT of 1.24 at 353 K and a high average ZT of 1.12 for temperatures in the range of 300–433 K in Bi2Te2.69Se0.33Cl0.03 + 1 wt% Ag8SnSe6, which are respectively ∼ 27.42% and ∼ 26.78% larger than those of Bi2Te2.69Se0.33Cl0.03. Furthermore, a device with two couples of n-p thermoelectric legs based on 1 wt% Ag8SnSe6 n-type legs shows a greater cooling temperature drop (28%) than that of the Bi2Te2.69Se0.33Cl0.03 n-type legs device. The high thermoelectric and mechanical performance (83.4 HV) of Ag8SnSe6 incorporation in n-type Bi2Te3 makes them strong candidates for practical applications.